Abstract:
Geophysical and oceanographic investigations were conducted in the Ross Sea during a McMurdo Sound to McMurdo Sound charter aboard the MV Benjamin Bowring. The main geophysical program was designed to study three regions in the Ross Sea including the Eastern Ross Sea basin and continental margin, the Western Ross Sea Graben and the Transantarctic Mountains front. The objective for the Eastern ... Ross Sea basin and continental margin was to complete gravity and seismic reflection and refraction data along profiles from the ice shelf to about 73°S along 170°W and 165°W. A link to the Deep Sea Drilling Program sites 270-272 would be made using existing Eltanin or Explora data. For the Western Ross Sea Graben, an east-west profile from 180° to 165°E along latitude 75.5°S was planned. Gravity and seismic reflection and refraction measurements were measured. For the Transantarctic Front, six east-west profiles about 30km apart running westwards from longitude 170°E to as near the Victoria Land coastline as ice conditions permitted was planned. Gravity and seismic reflection and refraction data were measured. The oceanographic program had two objectives, i) to sample the water mass at depths down to 300m to investigate the distribution of hard shelled phytoplankton between New Zealand and the Ross Ice Shelf, and ii) to obtain seafloor sediment samples along the ice front in McMurdo Sound. The plan was to consist of water bottle stations at every degree of latitude from 46°S to the edge of the Ross Ice Shelf, from Lyttelton, New Zealand to McMurdo Sound, and underway marine gravity measurements were planned for between bottle stations. On the voyage to McMurdo Sound, the oceanographic program and gravity measurements were carried out. The program consisted of water sampling to depths of 250m at station intervals of one degree latitude. However, rough sea conditions and violent ship motion curtailed the program and 8 stations were successfully completed. Gravity observations were made for most of the voyage but rough sea conditions shut down the meter for a couple of days and made data at other times marginal. Bathymetric data were recorded until depths of about 4000 m were reached when signal strength was too small and no record obtained. The results for the data collected from Lyttelton to McMurdo Sound includes 3700km of gravity measurements, 1000km of bathymetry measurements and 8 stations for oceanographic measurements. Due to ice conditions in the Ross Sea and equipment problems various measurements were collected for the Eastern Ross Sea basin and continental margin, the Western Ross Sea Graben and the Transantarctic Mountains front. Final results include 4200km of gravity measurements, 3200km seismic reflection profiling measurements, 25 sonobuoy seismic refraction observations and 6 shallow gravity core stations (5 successful).